| MicroRNAs is a class of?21 nucleotide single-stranded non-coding RNA molecules,which play important regulatory roles in animals and plants by post-transcriptionally regulate gene expression.In plants,microRNAs are involved in the regulation of cell division,meristem,organ boundary and leaf polarity development.MicroRNAs regulate targets by mRNA splicing,transcription silencing and translation inhibition.Brassinosteroids(BRs)influence plant responsiveness to the local environment and exquisitely promote,or interfere with,many aspects of plant development.In plants,BRs can contribute to the regulation of cell division and differentiation,promote catheter differentiation,improve the photosynthetic ability,influence pollen development and fertility,promote the regeneration and growth of seedlings,and enhance the resistance of plant.By earlier studying,Our laboratory got the 35S::MIR39X transgenic plants and found that 35S::MIR39X have the phenotypes of shortened hypocotyl,delayed flowering,rounder leaves,shortened petioles,down-curly cotyledon and so on.All above suggest that miR39x plays role in BR signaling.In this thesis,the functionary mechanism of miR39x and its target genes were studied.We mainly carried out these studying:1)the mechanism of how miR39x-BGP influence the response to BL of Arabidopsis thaliana,including the regulation of miR39x-BGP on BR signaling,the regulation of BR signaling on miR39x-BGP,the genetic analysis about miR39x and BR signaling components;2)the mechanism of how miR39x-BGP influence the response to GA of Arabidopsis thaliana,including the regulation of miR39x-BGP on GA signaling,the regulation of GA signaling on miR39x-BGP,the genetic analysis about miR39x and GA signaling components.Then we got the following conclusions:1)miR39x-BGP influence the sensitivity to BL in Arabidopsis thaliana.The hypocotyl length of 35S::MIR39X and BGP-RNAi bgp is shorter than Col-0 under LD condition,furthermore it has less sensitivity to BL and has more sensitivity to BRZ while mir39x ago 10 has less sensitivity to BRZ.It suggests miR39x-BGP influence the response to BR signaling in Arabidopsis thaliana.2)The expression of miR39x-BGP is regulated by BR signaling and miR39x-BGP regulate BR signaling.We tested if miR39x and BGP can induced or inhibited by BRs.The results showed that the GUS expression in pMIR39x::GUS can be induced by BRZ.The expression of BGP in bzrl-1D was up regulated and the expression of BGP in det2 was down regulated than Col-0.In order to analyze the probable molecular mechanism of affect on the BR signaling,the expression of DWF4 and PRE1 in 35S::MIR39X and BGP-RNAi bgp were analyzed,it showed that DWF4 was up regulated and PRE1 was down regulated in 35S::MIR39X and BGP-RNAi bgp compared to Col-0.These results showed that miR39x and BGP could influence the output of BR signaling,which would influence the hypocotyl elongation.3)In genetic relationship,miR39x is upstream of BIN2 and parallel with BSUl.In dark condition,the hypocotyl length of 35S::MIR39X×bril-5 is shorter than 35S::MIR39X and bri1-5;With the treatment of BRZ,the hypocotyl length of 35S::MIR39X×35S::BSU1-myc was higher than 35S::miR39x transgenic lines and lower than 35S::BSU1-myc,which indicated that the miR39x and BSU1 was parallel in genetics;the hypocotyl length of 35S::MIR39Xxbin2-3 bill bil2?35S::MIR39X×bzrl-1D?35S::MIR39X×besl-D was similar to bin2-3 bill bil2?bzrl-1D?besl-D,which indicated that the miR39x was upstream ofBZR1 in genetics.4)miR39x-BGP influence the sensitivity to GA in Arabidopsis thaliana.The seedings of35S::MIR39X and BGP-RNAi bgp or bgp mutant were treated with GA or PAC,it showed that the sensibility to GA of 35S::MIR39X transgenic plants and bgp is declined.Further test shows that 35S::MIR39X and BGP-RNAi bgp transgenic plants enhanced sensibility to PAC,and mir39x ago10 declined the sensibility to PAC,suggesting that miR39x-BGP regulates the response to GA signaling.5)The expression of miR39x-BGP is regulated by GA signaling and miR39x-BGP regulate GA signaling.The GUS expression in pMIR39x::GUS can be also induced by PAC.The expression of BGP in rga-24 gai-t6 was up regulated.In order to analyze the probable molecular mechanism of affect on the GA signaling,the expression of GA3OX1 in 35S::MIR39X and BGP-RNAi bgp were analyzed,it showed that GA30X1 was down regulated in 35S::MIR39X and BGP-RNAi bgp compared to Col-0.These results showed that miR39x and BGP could influence the output of GA signaling.6)In genetic relationship,miR39x is upstream of DELLA.With the treatment of PAC,the hypocotyl length of 35S::MIR39X×rga-24 gai-t6 was similar to rga-24 gai-t6.which indicated that the miR39x was upstream of DELLA in genetics. |
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